Ray Tracing Simulation of a GaN-based integrated LED-Photodetector System

An optical sensor system consisting of a pair of GaN LED and Photodetector (PD) is simulated using COMSOL Multiphysics, and the possibility of using this system as absorption coefficient sensor is studied. By locating both LED and PD on a same substrate and measuring transmitted power to the PD, it would be possible to sense changes in the optical parameters of the transmission path. In the present work, the gap between LED-PD pair is filled with an ink, and the optical extinction coefficient of the ink is monitored by measuring transmitted power from the LED to the PD.